Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210252 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1052 PM EDT MON APR 20 2015 .SYNOPSIS... A COLD FRONT WILL PUSH EAST ACROSS THE REGION DURING THE OVERNIGHT HOURS. AN UPPER LOW WILL THEN PERSIST ACROSS THE GREAT LAKES TO NEW ENGLAND THROUGHOUT THE WEEK. && .NEAR TERM /THROUGH TUESDAY/...
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TORNADO WATCH WAS ALLOWED TO EXPIRE AT 10 PM EVERYWHERE EXCEPT MARINE ZONES WITH DIMINISHING SEVERE THREAT. SCT SHOWERS WILL CONTINUE TO OCCUR AS A COLD FRONT MOVES EAST ACROSS THE REGION...MAINLY THRU 07Z. LATEST WATER VAPOR IMAGERY SHOWING GOOD AMT OF DRIER AIR IN THE WAKE OF THE FRONT...SO EXPECTING PCPN TO END WITH FRONTAL PASSAGE. DP UPR LOW WL RESIDE NORTH OF THE GRTLKS TMRW...WHICH WL PROVIDE FAST MID-LVL FLOW. KEEPING A DRY FCST W/ CLDY PERIODS AS IMPULSES ZIP THRU THE FLOW. DOWNSLOPING WL PROVIDE THE WARMING IN SPITE OF CAA.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... NOT MUCH OF A BREAK BETWEEN SYSTEMS AS THE MID-ATLC STAYS JUST ON THE OUTER FRINGE OF A LARGE UPPER GREAT LAKES TROUGH. ONE OF THE WEAKER VORTS SLIDING AROUND THE BASE OF THE TROUGH WILL SLIDE INTO THE WINDWARD SIDE OF THE APLCNS LATE TUE NIGHT. LITTLE MORE THAN COOLER AIR WILL MAKE IT OVER THE MTNS...W/ THE MOISTURE DISSIPATING OVER THE HIGHER TERRAIN. HEADING INTO EARLY WED...A STRONGER LOW PRESSURE SYSTEM WILL BE DEVELOPING WELL TO OUR NORTH WHICH WILL ALSO STRENGTHEN THE INCOMING COLD FRONT. GUSTY SW WINDS WILL ARRIVE BEFORE ANY PRECIP E OF THE APLCNS...AND GRADUALLY PULL UP OUR COOL TEMPS FROM OVERNIGHT BACK INTO A WARMER REGIME BY MIDDAY. UNLIKE TODAY`S CONDITIONS...THIS FRONTAL PASSAGE IS NOT EXPECTED TO MUSTER UP MUCH INSTABILITY. THE SRN HALF OF THE CWA MAY SEE SOME WEAK CONVECTIVE POTENTIAL BUT THE REMAINDER OF THE AREA WILL SEE AT SOLID CHANCE FOR RAIN SHOWERS. TEMPS WILL BE ABOVE AVG FOR THE VA/MD PIEDMONT. QPF FAIRLY LIGHT FOR THIS PASSAGE AND A RELATIVELY BRIEF PERIOD OF THE MID AFTN TO EVE. BY LATE EVE...MOST OF THE PRECIP WILL BE SLIDING OUT OF THE SE PORTION OF THE CWA AND CLOUDS WILL ALLOW EXIT OFF THE COAST. && .LONG TERM /THURSDAY THROUGH MONDAY/... LONG TERM PERIOD WILL BE DOMINATED BY A COLD UPPER-LEVEL LOW PRESSURE SYSTEM STALLED OVER THE NORTHEASTERN CONUS...WITH PERSISTENT CHILLY WEST OR NORTHWEST FLOW OVER THE REGION. A TROUGH MAY BRING PRECIPITATION TO THE AREA SATURDAY...BUT OTHER THAN THAT IT LOOKS MAINLY DRY. TEMPERATURES WILL BE WELL BELOW NORMAL /I.E. 10-15 DEGREES BELOW NORMAL/ THROUGH THE PERIOD WITH HIGH STRUGGLING TO GET OUT OF THE 50S AND LOWS IN THE UPPER 30S TO 40S. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... MAINLY VFR CONDITIONS THROUGH THE TAF PERIOD. ISO SHOWER/TSTM STILL PSBL THRU 07Z AS COLD FRONT MOVES THROUGH...WITH DRY CONDITIONS THERE AFTER. ANY TSTM COULD PRODUCE A GUST UP TO 35 KT. OUTSIDE OF PCPN...WINDS MAINLY SLY AROUND 10 KTS...BCMG WLY LATE TONIGHT. WIND SHIFT COULD BE DIFFERENT 1-2 HRS. WLY WINDS OVNGT THRU TUE...W/ GUSTS UP TO 25 KT DURING THE DAY. ANOTHER COLD FRONT WILL SWING THRU ON WED AFTN. GUSTY SW WINDS AHEAD OF THE FRONT AND MAINLY BRIEF/SCTD SHOWER ALONG THE BOUNDARY AS IT SLIDE THRU DURING THE 2ND HALF OF THE DAY. WLY FLOW 10 KT OR SO W/ MAINLY VFR EXPECTED THU-SAT. && .MARINE... SCA REMAINS IN EFFECT FOR ALL WATERS...WITH THE UPPER TIDAL POTOAMC ENDING AFTR 05Z. GUSTS INCREASE AGAIN AFTR DAYBREAK TUES...SO SCA WILL BE BACK IN EFFECT FOR UPPER TIDAL POTOMAC...ALONG WITH THE REMAINING WATERS. SOLID SCA WINDS POSSIBLE ON WED AHEAD OF AND ALONG A COLD FRONT THAT IS EXPECTED TO SWING THRU THE WATERS BY LATE EVE. SCA GUSTS POSSIBLE IN WLY SURGE BEHIND FRONTAL BOUNDARY THURSDAY...THEN LIGHTER FLOW BELOW SCA CRITERIA LIKELY FRIDAY- SATURDAY. && .TIDES/COASTAL FLOODING...
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MINOR COASTAL FLOODING OCCURRING ALONG THE POTOMAC RIVER NEAR ALEXANDRIA...SO HAVE ISSUED AN ADVISORY TO ACCOUNT FOR THIS THRU MIDNIGHT TO HANDLE THE HIGH TIDE CYCLE. EXPECTING LVLS TO DROP THERE AFTER. THE COASTAL FLOOD ADVISORY WAS CANCELLED FOR THE CHESAPEAKE BAY WITH TIDE LVLS BARELY REACHING ACTION STAGE AT THE TIME OF HIGH TIDE. WITH WINDS SHIFTING TO THE W FOR TUES...NOT ANTICIPATING ANY FURTHER CONCERNS AFTER TONIGHTS CYCLE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR VAZ053- 054. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY UNTIL 1 AM EDT TUESDAY FOR ANZ535-536. SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT TUESDAY FOR ANZ535- 536. COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ535.
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